[Dovecot] Can't start dovecot from heartbeat

[John Gray]

I get the following error:

Fatal: epoll_create(): Too many open files (you may need to increase
/proc/sys/fs/epoll/max_user_instances)

Works fine if I start it by hand, I'm guessing it has to due with the
environment heart starts it in?

My first thought was to do exactly what the message suggests, but my
kernel doesn't appear to define max_user_instances, but there is a
max_user_watches.

I'm running 1.2.8, by the way.  But I had a similar problem with earlier
version too.

John